CSUN Prof’s Research Provides Insight into Neandertal History
More than 100 years after archaeologists discovered the remains of Neandertals in caves in Belgium, California State University, Northridge associate anthropology professor Hélène Rougier re-examined the debris from those remains, and her findings are helping to shed light on the history of Neandertals living in Eurasia 39,000 to 47,000 years ago.
Rougier is part of an international, interdisciplinary team of researchers who have been able to sequence the genomes of five Neandertals. That information — when studied alongside the genome sequences generated since 2010 from the remains of four other Neandertals found in Croatia, Siberia and the Russian Caucasus — is helping the researchers begin to reconstruct Neandertal history.
“We got DNA from five individuals from five different places that cover a large territory,” Rougier said. “One of the interesting results we found, when you look closely at the genetic material, is the relationship between the remains. My geneticist colleagues were able to demonstrate the genetic connection between remains found hundreds of miles apart in different regions of the continent.”
That discovery, Rougier said, has researchers pondering Neandertal populations’ movement and interaction, including how one population of Neandertals replaced another.
“We don’t have all the dots yet,” she said, “but what we are finding is providing us with insight into the history of Neandertal populations, and how they interacted. It’s really a work in progress. We’re just adding more and more data that will someday offer more detailed insight into these populations.”
The results of their research, “Reconstructing the genetic history of late Neandertals,” have been published in Nature. Rougier was one of 31 researchers from around the world working on the project. Their disciplines crossed the spectrum, from anthropology and archaeology to biology and genetics.
Rougier said the interdisciplinary approach to the research provided an opportunity to bring new perspectives and raised questions that individuals in a particular specialty may not have considered.
As part of the project, Rougier painstakingly searched through artifacts recovered from two caves in Belgium, one, Spy, where, more than 100 years ago, archaeologists found Neandertal remains. The other, Goyet, where human remains were discovered in 1868 by a geologist, but were not identified as Neandertals until Rougier worked on the collection.
The first time the caves were excavated was the end of the 19th century, Rougier said.
“At that time, they didn’t use the methods we use today, and they were less careful than we are now,” she said. “They discovered the remains of two Neandertals. When they were discovered, they were the first Neandertals to be discovered in place.”
Prior to that, Rougier said, workers discovered the remains of a Neandertal in Germany, brought the bones to scientists, but were unable to say specifically where they made their find.
In this particular Belgium cave, Rougier said, two 19th century researchers intentionally dug deep in the cave’s floor looking for artifacts, and found the remains of two Neandertals.
“The idea was to make an archaeological discovery, and they did,” she said. “So, we knew where the bones came from. That was a big deal at the time.”
Over the years, the site was excavated several times. In the later 1940s and early 1950s, a researcher used a sieve to collect and preserve a wider range of materials. His finds were stored in a museum relatively untouched until Rougier and a colleague started to sort through countless drawers of bits and pieces of what was believed to be animal bones, ivory and other materials.
After days and days of careful sorting, they found not only pieces of bone belonging to the two Neandertals initially found in the Spy cave, but also bone fragments belong to a third Neandertal. These new remains had not been treated, allowing the researchers to directly date these individuals and show that they were all late Neandertals from near the end of the Neandertals’ existence.
Inspired, Rougier organized a team to re-assess items collected from the Goyet cave not far from the one where the 19th century archaeologists made their find. Using an interdisciplinary approach, they sorted through the collection to identify new human remains and then made biogeochemical analyses, they again found bone fragments. Similar methods were used by researchers with remains in France, Croatia and the Caucasus. The researchers selected the remains of five individual Neandertals for future genetic analysis.
Geneticists were able to sequence the genomes from the five Neandertal remains — the two Rougier identified from the caves in Belgium and three from sites in France, Croatia and the Caucasus — doubling the number of Neandertal remains for which genome sequences are available.
“When you talk to geneticists today, they are even surprised at what they can do,” Rougier said. “Ten years ago, they didn’t think they would be able to retrieve DNA like this.”
Having genomes from multiple Neandertals provided the researchers a foundation from which to begin reconstructing Neandertal population history. They were able to see genetic similarity between the Neandertals that correlated with their geographic location.
They also were able to compare the genomes of the late Neandertal remains to the genomes of an older Neandertal from the Caucasus that seem to indicate that Neandertal populations moved and replaced each other toward the end of their time on Earth.
The team also compared the Neandertal genomes to the genomes of people living today, and they found that all of the late Neandertals were more similar to the Neandertals that contributed DNA to present-day people living outside Africa than an older Neandertal from Siberia. Even though four of the Neandertals lived at a time when modern humans already had arrived in Europe, they do not carry detectable amounts of modern human DNA.
“It’s really interesting to be an anthropologist right now,” Rougier said. “We’re getting sources of information that we didn’t have before. We’re starting to have information at a more intimate scale that we never had before. And it’s giving us greater insight into who the Neandertal were and what they did.”